Group III-nitride semiconductors have been commercialized as light emitting devices such as blue light emitting diodes (LED) and blue-violet semiconductor lasers (LD). In light emitting devices using a group III-nitride semiconductor, a luminous efficiency decreases as the wavelength becomes longer than blue light, so the luminous efficiency of a green light emitting device, for example, is significantly lower than the luminous efficiency of a blue light emitting device.